1. Field of the Invention
The present invention relates generally to switching devices. More particularly, the present invention relates to an optical switch for selectively redirecting one or more beams of data transmitting light carried by one or more light transmitting input conduits to one or more light transmitting output conduits.
2. Background of the Invention
Today""s high speed communications systems commonly employ fiber optic communications channels with electronic switches and routers. However, the combination of optical data transmission and electronic switching requires numerous optical-to-electrical-to-optical conversions. This is costly in terms of bandwidth limitations, power consumption, size of system components, and overall system throughput.
At the core of today""s network is the switching fabric. A major function of the switch is to reroute optical signals from an array of input fibers to an array of output fibers. Switches currently in use require conversion of the optical signals received on fiber channels into electrical signals, electrically routing these signals, and then converting them back into optical signals and launching them into the fiber channels. This complex set of conversions creates significant overhead in terms of power, data throughput, and latency. Such switches are blocking (i.e., disallow signal fan-out and fan-in) and are non-transparent (i.e, the signal does not stay in optical form). Also the bandwidth (data rate) of the signal must be within that of the electronic switch, which can be orders of magnitude less than that of the optical signal. Thus, the router becomes the system""s bottleneck.
What is needed, therefore, is an improved optical switching device that avoids bandwidth and other limitations present in electro-optical switches.
The present invention eliminates the difficulties and disadvantages of the prior art by providing an optical cross connect switch that is capable of optically transferring optical beams propagating in an input optical fiber to one or several output optical fibers. The optical cross connect switch can be designed such that it distributes the optical signal propagating in either one or several input optical fibers to either one or many output optical fibers in any predetermined combination. Additionally, the optical cross connect switch of the present invention can be programmed for any specific optical connections that are to be formed between input and output optical fibers.
The optical cross connection switch of the present invention can be used in the switching fabrics of fiber optic networks. The optical cross connect switch removes the bottleneck of converting light signals into electrical signals and back into optical signals. Additionally, the present invention can be used in switching and routing circuits for many different types of fiber optic networks.
Additionally, the optical cross connect switch of the present invention may use microelectromechanical systems (MEMS), diffractive, reflective and refractive optical elements and fibers. The use of MEMS devices can allow the optical cross connection switch of the present invention to be made compact in size, can decrease the power consumption needed to switch the optical signals, and switch the optical signal at a relatively high speed. Further, the use of diffractive optical elements provides the capability of switching the optical signal in a flexible way. Further, the diffractive optical elements may minimize signal loss caused by coupling. Also, because the present invention uses optical rather than electrical switching, the switching time is typically less dependent on the size of the network (i.e., the number of input and output fibers).
This invention introduces a new approach to implement a transparent all-optical, non-blocking crossconnect switch for routing optical network traffic. This approach is based on the combination of MEMS, diffractive optical elements, and optical fibers. The current invention can be used in the switching fabrics of fiber optic telecommunication as well as computer networks. It can remove the bottlenecks of converting between optical and electrical signals and the bandwidth limitations of current electro-optic switches. Additionally, the present invention can be used in switching and routing circuits for many types of fiber optic networks since it is protocol independent. It is not limited to today""s Synchronous Optical NETwork (SONET) and Synchronous Digital Hierarchy (SDH) data streams, but can also just as easily carry protocols such as Asynchronous Transfer Mode (ATM), Internet Protocol (IP), and Gigabit Ethernet. Compared to mirror-based MEMS switch approaches, the proposed switch needs far fewer actuators, which enhances size, yield, cost, and power consumption. Also, it has improved optical coupling efficiencies. In addition, the present invention may offer significant reconfiguration speed and routing flexibility advantages.
The present invention is implemented using several exemplary embodiments each of which uses diffractive, refractive or reflective optical elements to route the light signals from the input to the output fibers. Diffractive optical elements (DOE) provide a better alternative to mirror based routers because of their high diffraction efficiencies (which can result in very low coupling losses) and functional flexibility in combining multiple optical functions in a single DOE element. This eliminates the need for GRIN or ball lenses and also allows routing the optical beam from a single input fiber to multiple output fibers simultaneously.